On-site preconcentration and trace metal ions determination in the Okavango Delta water system, Botswana

Abstract

Microcolumns containing 8-hydroxyquinoline azo-immobilized on controlled pore glass were incorporated in a field sampler for on-site collection, isolation and preconcentration of trace metal ions in waters of the Okavango Delta, Botswana. Sequestered trace metal ions were recovered by elution with 0.5 ml of 1.5 M nitric acid, and determined by graphite furnace atomic absorption spectrometry (GFAAS). This sampling and enrichment method minimizes sample contamination, and collection of large volumes of water samples for transporting, over long distances, to analytical laboratories is avoided. Data reported comprise one of the initial surveys on trace metal ion concentrations in waters of the Okavango Delta, Botswana. In waters with more efficient mixing, dissolved metal ion concentrations found were generally low with slightly elevated levels of manganese (7–19 μg l −1 ), zinc (2.7–4.8 μg l −1 ), nickel (0.2–2.5 μg l −1 ) and copper (0.3–2.1 μg l −1 ). For each trace metal ion, concentration levels seem to reflect zones of varying water conveyance, and show no obvious temporal and spatial variations apart from a slight increment from the inlet in the upper Delta to the outlets in the lower Delta.